The invention relates to a conductivity strap arrangement and more particularly, to a conductivity strap arrangement for use with a valve having a non-conductive valve gate.
Public water supply systems include underground piping to direct pressurized water throughout a community. This piping typically includes a number of manually operable valves located at multiple locations throughout the system to selectively control water flow through the piping. While the vast majority of the piping is buried and inaccessible, the valves are located within access passages that typically are enclosed by a removable manhole cover or curb-box cover. To actuate the valve, long steel valve wrenches are provided which allow a utility worker to place a valve wrench on the operating nut of the valve when the utility worker is at ground level. The utility worker can turn the valve wrench from ground level to open and close the valve.
During operation of the system, it may be necessary to either locate the piping below ground such as for repair work or laying of new utilities. Also, during extremely cold conditions, piping may become frozen and it would then be necessary to thaw the blocked piping.
A common practice for locating and/or thawing piping is to apply an electrical current to the piping which current flows through the piping and can either be detected for locating purposes or causes heating of the piping due to the resistance of the metal pipe material. Therefore, during installation of a piping system, the water supply system typically is designed to permit current flow therethrough.
Many gate valves used in such systems include a conductive valve gate. This valve gate is connected to the metal operating nut on the valve through a conductive valve stem while the valve itself is connected to the metal piping. Therefore, it is a common practice to place the metal valve wrench on the operating nut and apply a current to the valve wrench, for example, by the connection of a welder or a car battery charger directly to the exposed upper end of the valve wrench. This applies a current to the valve wrench and therefore to the valve which current then is able to flow to the piping connected to the opposite ends of the valve.
Away from the valve area, metal-to-metal contact may be present between two sections of piping at a joint therebetween, such that the current is able to flow directly from one pipe section to another pipe section. However, some pipe sections are joined together by compression fittings which compression fittings may break the conductivity path. Accordingly, for such fittings, it also is known to connect opposite ends of a conductivity cable to individual pipe sections to ensure that a conductive path extends between the pipe sections adjacent to the fitting.
While such systems are known, another type of gate valve uses a non-conductive valve gate, for example, where the valve gate is coated by a non-conductive material. The non-conductive valve gate thereby breaks the current path which otherwise would extend from the operating nut to the valve body.
It therefore is an object of the invention to overcome the disadvantages associated with using a nonconductive gate valve in a water system.
The invention relates to a conductivity strap arrangement which allows for the flow of current from an operating nut of a non-conductive valve to the adjacent pipe sections connected to the valve. The conductivity strap arrangement generally includes a conductivity strap having lugs at the opposite ends of a flexible strap section wherein the lugs are electrically connected to the adjacent pipe sections. The strap section of the conductivity strap mounts to the valve stem so that a current applied to the operating nut through a valve wrench thereby is able to flow to the adjacent pipe sections.
Preferably, the conductivity strap is formed of a stranded conductive material which does not have a performed hole in the intermediate portion of the strap. Rather, the strands of conductive material may be separated during installation and pressed onto the upper end of the valve stem. Preferably, the strands are braided or intertwined. In this manner, the valve stem spreads the strands of the conductive material apart from each other to form a hole in sit-up. This is particularly advantageous since the separated braids of the strap provides a tight gripping fit with the valve stem and provides firm conductive contact therebetween.
Additionally, the opposite ends of the strap may be pulled longitudinally which tightens the braided strands about the valve stem to improve contact of the strap with the.exterior surface of the valve stem. The lugs at the opposite ends of the strap are fixed to a locking gland or collar used to join the adjacent pipe sections together. Since the valve stem and the operating nut are both formed of metal, current applied through the steel valve wrench flows through the operating nut to the valve stem and thereby flows through the conductivity strap.
With this arrangement, non-conductive gate valves can be readily used as current input locations by use of an inexpensive conductivity strap that may be readily installed merely by removing the operating nut.